[Question] `zero_agent.py` cannot work as excepted

[Tristean]

Describe the bug

I attempted to create a new multi-agent external project using ./isaaclab.sh --new. The project configuration specifies skrl as the RL library and MAPPO as the selected RL algorithm. However, when executing python scripts/random_agent.py --task=<TASK_NAME>—as instructed in the README.md—the script fails with the error shown below:

Steps to reproduce

1. Run ./isaaclab.sh --new.
2. Select External as the task type.
3. Specify project_path, project_name, and choose Direct | multi-agent for the Isaac Lab workflow.
4. Set rl_library to skrl and RL algorithms for skrl to MAPPO.
5. Install the generated package in development mode (python -m pip install -e source/xxx) and execute python scripts/zero_agent.py --task=<TASK_NAME>.

System Info

Describe the characteristic of your environment:

• Commit: f3decd9
• Isaac Sim Version: 5.1
• OS: Ubuntu 24.04
• GPU: RTX 4060
• CUDA: 13.1
• GPU Driver: 590.48

Additional context

This issue is specific to multi-agent configurations,it does not occur when generating a single-agent external project. Investigation reveals that the env object in multi-agent mode lacks an action_space attribute—whereas this attribute is present and accessible in the single-agent env instance. This suggests a structural divergence in the env variable between the two modes. This issue also happens if run the command python scripts/random_agent.py --task=<TASK_NAME>

`action_space` exist in `single_agent`

no `action_space` exist in `multi_agent` mode

Checklist

• I have checked that there is no similar issue in the repo (required)
• I have checked that the issue is not in running Isaac Sim itself and is related to the repo